Acoustic tile



Patented Sept. 17, 1935 UNITED STATES ACOUSTIC TILE Herbert C. Smith,Los Angeles, Calif., assignor to Coast Insulating Company, a corporationof Delaware Application February 1, 1933, Serial No. 654,676

12 Claims.

The present invention relates to sound absorbing material and moreparticularly that type of product known as acoustic tile an-d which isadapted to complete manufacture prior to being applied to wall orceiling.

An object of the invention is the provision of a highly efcientsound-absorbing tile provided with a durable exterior surface which maybe painted or otherwise decorated without altering the eiiiciency of thetile as a Whole.

One type of acoustic tile employed in present practice is a perforatedpan or box lled with sound absorbing material which lies -directly overthe openings. The exposed area of material is of course limited to theextent of the total area of the perforations. This requires scientificspacing of the apertures with respect to their diameters and bestresults are ha-d only when the diameter of the apertures is less thanthe spaces between them; this resulting in considerably less thanone-half of the total area of the tile presenting sound absorbingmaterial directly to sound waves.

My invention provides a tile having an exposed metal surface which isperforated but there is, practically speaking, no limit to the totalarea which the perforations may occupy and in fact the invention permitsof having the diameter of each aperture greater than the distancebetween two adjacent apertures. The invention is further distinct inthat it provides for exposing to the soun-d waves a total soundabsorbing surface greater than the total area of all perforationscombined an-d in fact greater than the total area of the tile. v Anothertype of tile presenting increased surface is composed of fibrousmaterial worked into a composition board of relatively great density ascompared with other well known sound absorbing media, and the outersurface of this board is perforated with drill holes running into theinterior structure.

It is an object of the present invention to provide a tile presenting aperforated metal face; the perforations of which communicate with deepholes extending inwardly through a very resilient and porous soundabsorbing material contained behind the metal face. Another object ofthe invention is to dispense with the cost and disadvantage of drillingthe holes since drilling operations are expensive; the walls of adrilled hole are usually less porous than th-e structure in which thehole is drilled; chips may remain which later filter out and becomegenerally troublesome; and, it is another object of (Cl. Y2-18) theinvention to employ material that is so resilient and porous and sohighly eicient acoustically as not to even permit of being drilled.

In fact the invention provides, and it is an object of the invention toprovi-de, an acoustic 5 tile which while distinct from previous typespossesses in addition to unique advantages of its own the advantagesascribed to the aforesaid types without the use of the structuralfeatures of either. 10 Finished appearance and properly concealedanchorage, at minimum expense, is another object of the invention.Composition board, unless the edges are carefully finished does notprovide the finished appearance that I desire to 15 j obtain by thisinvention whereas the metal box type of tile with its looselyarticulated contents does not permit of being attached to a ceilingexcept by the use of complicated and costly aty taching means; usuallyin the form of tracks in 20 which boxes or pans are suspended. A

In this connection it is another object of my invention to not onlyprovide a tile of finished appearance and properly abutting edges, butto provide a tile which while containing a loosely 25 articulated soundabsorbing material is of great structural strength and which may benailed or glued in place at minimum expense, and in such manner that allanchorage is concealed.

Other objects of the invention include; re- 30 proof qualities;inorganic material; -durability to permit of stacking, packing andshipping; mass production methods for manufacture and low costthroughout.

In many applications of my tile toe-nailing 35.

may be employed to anchor same altho the in-v vention provides that thetile may be secured by nails driven directly through the tile from theouter surface without the nail being exposed to view.

As a rule, the more eicient a sound absorbing material, the greater itsfirst cost. An object of this invention is to provide for maximum soundabsorbing surface with the minimum of material and with the use of thehigher grades of mate- 5 rial. Through my invention there can be no lossof material by reason of waste material from drilled holes, while thetotal Volume or bulk of material used is less, with respect to the totalexposed surface area than in the present types 50 of acoustic tile.

In this connection I have discovered that whereas in sound absorbingmaterial laid parallel to a wall surface a given depth is required tomeet the usual requirements and speciiications; 5:75-l

it is possible to obtain results with a lesser bulk of material byhaving surfaces of the material disposed at right angle to the wall orceiling. In a tile measuring 12 inches by 14 inches and having a totalbulk of 168 cubic inches it is possible to have as much as 500 squareinches of exposed sound absorbing surface or three times as much as thesurface area; which is equivalent to obtaining all the benefits of oneinch thickness of material with the use of only enough material tospread over the ceiling or wall surface to a depth of one-third of aninch in thickness.

Expressed in still other terms, I have discovered that where a mass ofsound absorbing material provides opposed surfaces extending normally ofthe wall surface, and both surfaces of the material are exposed to soundwaves, a given sound absorbing result can be obtained with less bulk ofmaterial, or less depth between the two surfaces than would be the depthof material required between one sound absorbing surface and a solidwall surface.

My invention While broad in its scope and not limited to the structureabout to be described, is more readily understood from an explanation ofone practical embodiment thereof; said embodiment being shown in theaccompanying drawing in which:

Figure 1 is a vertical sectional view showing a plurality of oneembodiment of tile applied to a ceiling.

Figure 2 is a face view of the tile.

Figure 3 is a vertical fragmentary section of the tile in the act ofbeing manufactured; the view showing certain moulding appliances used inconnection therewith.

Figure 4 is a fragmentary face view of a modified form of tile andFigure 5 is a cross section on line 5 5 of Figure 4.

More specifically, Figure 1 indicates a metal box or pan having a bottomwall, 1, provided with closely spaced and relatively large apertures, 8;the latter preferably so arranged that the maximum distance from twoadjacent margins of spaced openings is not greater than the diameter ofthe openings itself and so that the total area of openings is equal toat least the area of the remaining metal. The box is further providedwith encompassing vertical side walls, 9, 9, etc.; the latter beingimperforate except for a nail hole such as I0 in each side wall.

The box is formed with beveled edges to give the proper appearance tothe finished tile and either before or after application to a ceilingsuch as II, the outer surface I2 of the box may be suitably decorated.It is understood that the arrangement of apertures 8; their spacing andsize, is such that a great multiplicity of them appearing in anotherwise co-extensive surface does not prevent carrying out anydecoration scheme and the individual apertures do not appreciablydetract from the appearance of a co-extensive surface. It is alsoprovided that the material visible slightly through the apertures may beof the same color as that of the surface I2 of the box.

In the manufacture of the tile, I provide a matrix consisting of a baseplate, I4, provided with a multiplicity of vertical core pegs, I5; onefor each of the many apertures in each tile. The box is placed withsurface, I2, in contact with the base plate, I4, so that each aperture,8, is closed by a corresponding peg which extends into the interior ofthe box a suitable depth. The pegs are preferably slightly tapered andterminate slightly below the upper edges, I6, of the box.

With the box in such position it is filled to a point just above thepegs with the sound absorbing material, I'I. This may be any mixture ofsuitably porous material and a binder, such as pellets of pumice with abinder, mica composition or ex-foliated vermiculite; asbestos fibre witha binder, or mineral wool in any of the usual commercial forms with abinder comprising just enough silicate of soda to hold the material inplace without detracting from its high sound absorbing values. As willappear hereinafter the structural strength of the tile as a whole is notin any way dependent upon the material, I'I.

It will be apparent now that the total volume of space between pegs isconsiderably less than the total Volume of the box and that lessmaterial is employed than if the box were without the pegs. ployed asfor instance in the case of mineral wool short fibres in the form ofshredded or balled wool Imay be used in place of the usually moreexpensive pads or quilts.

When the box has been practically lled with the material, II, a moredense molding material, or the like, is placed in the upper part of thebox overlying the material, I'I, as at I8. The material should be ofsuch strength as to form a top wall and a top surface, I9, for the box.This may erably, the material should present the surface,

I9, of such nature that it may be glued or cemented to another surfaceand it should not be dense enough to detract rfrom sound absorbingqualities. The wall, I8, of the box now becomes a part thereof; becomingjoined or bonded to the side metal walls, 9, 9, etc.

The tile, immediately after the material, I'I, and the material, I8, arein place, may be removed from the matrix and set aside to dry untilcured. The nature of the binder used depends upon the time required fordrying and also determines how quickly the tile may, or should be,removed from the matrix.

When the tile is finished by drying the space taken up by each pegduring molding leaves the corresponding deep cavity, 20, alined with thecorresponding aperture and having a total surface, 2i, of far greatertotal area than that of the aperture, 8.

The material between the cavities is of lesser 'v thickness than thetile as measured normally to the surface, 8, and the total area ofsurfaces of the cavities may be many times that of the total area oftile surface and apertures combined, while the total volume of thecavities is about onehalf the total cubic contents of the tile.

By reason of the tapered pegs the material between cavities is ofslightly increasing thickness upwardly while the surfaces of thecavities are slightly declined from the vertical.

Sound waves rising directly normal to the surface of the tile will enterthe cavities and strike either the declined side walls thereof or strikethe very innermost end of the cavities while those reaching and enteringthe apertures at ar1- gles are reflected further inwardly` Those skilledin the art will realize at a glance that the total area and relativedisposition of the surfaces surrounding the cavities is conducive tohigh sound-absorbing efficiency while those Also less expensive materialmay be em skilled in the manufacturing arts to which this appertainswill realize that low manufacturing cost and high-speed production ispossible by reason of this invention.

The modification shown in Figures 4 and 5 shows the apertures ofhexagonal shape and since the cavities are produced by moulding there isno limit to the shapes that may be employed. By using the hexagonalshapes and the spacing shown, the remaining metal surface of the box iscomposed only of interconnected strips of material and the material, I1,forms itself into a crossing arrangement of relatively thin dependingcurtains which by reason of the structure of the tile as a whole areheld substantially while having all the advantageous properties forwhich they are intended.

Thus it will be seen that by using relatively large openings and closespacing and great cavity depth, the total area of apertures may be asgreat or greater than the area of the unperforated surface of the tilewhile the total internal surface area of the cavities may be many timesthat of the total area occupied by the tile.

While the top wall of the tile permits of same being cemented or glueddirectly to a surface, and While the tile may be caused to adhere evento a ceiling surface by setting it in place while the composition of thetop wall is still tacky enough to hold, and so that the tile may cureWhile in place, it is also possible to keep the tile in stock and latersecure them in place by nails such as 2| or 22.

The nail, 2 I, is driven into an aperture, and then by the use of asuitably long center punch (not shown) may be driven home until it isout of sight and until its head abuts the more dense material, I8. Oragain, the tile may be secured as by toenailing with the nail, 22,passing obliquely through the aperture therefor provided as at l0 in theside wall, so that the nail passes through the structure and into theceiling or Wall to which the tile is applied.

Considering the finished product structurally, the perforated bottomWall, the imperforated side walls which are an integral part of the box,and the moulded top wall which becomes substantially an integral part ofthe box, form a complete six sided hollow box of light weight, low costand great strength. The remaining interior volume is occupied by arelatively resilient structure of the material, I6, which is held gentlybut immovably between the top and bottom walls and this structure iscellular both by reason of the cellular material of which it is composedand by reason of the great multiplicity of outwardly opening cavitiesalining with the apertures in the bottom or outer wall.

The tile may be handled and nailed as freely as if it were one solidpiece and in fact more so since while equally as strong it is not givento splitting, warping or other deformation to which solid mouldedproducts are inclined.

The invention is not limited to the specific structures and materialsmentioned herein and is of a broad nature; the scope of the inventionbeing set forth by the appended claims.

I claim:

l. In an acoustic tile, a hollow metal box comprising integral sidewalls, an integral perforated bottom wall and a substantially integraltop wall, the walls enclosing a cellular sound-absorbing materialnormally unsuited to direct exposure contained in the interior of saidbox, the cellular material being provided with a plurality of moldedcavities corresponding in number and spacing to the perforations in saidbottom wall, each cavity in communication with a correspondingperforation and presenting an internal wall surface of greater area thansaid perforation.

2. In an acoustic tile, a hollow box comprising rigid bottom, top andinterconnecting side walls respectively providing a hollow interior, thebottom wall being provided with a plurality of closely spacedperforatigns communicating with said interier,v andacellla`r"`s'ound-absorbing structure normally unsuited to directexposure contained in said interior, said structure provided with aplurality of deep cavities moulded in said material, the cavitiescorresponding in number and spacing to the perforations with each cavityin direct communication with the corresponding perforation, the cavitiesproviding a total internal wall surface area greater than the total areaof said bottom wall.

3. In an acoustic tile, a metal box having a bottom wall provided withclosely spaced apertures, vertical side Walls to said box, a cellularsound absorbing material in said box overlying said bottom wall, and adenser material molded in said box over said cellular material andforming a top wall to said box joined to said side walls, the cellulai1sound absorbing material being moulded with a plurality of deep cavitiescorresponding in number and spacing to said apertures and each cavity indirect communication with the corresponding aperture, the total of allcavities providing a combined internal wall surface area greater thanthe area of said bottom wall.

4. In an acoustic tile a metal bottom Wall provided with closely spacedapertures, encompassing side walls rising from said bottom wall, angularindentations in said side walls providing for nailing the tile to aceiling, and a mass of cellular material in the space enclosed by saidwalls, said material being of lesser structural strength than thematerial of said walls.

5. In an acoustic tile a metal bottom wall provided with closely spacedapertures, encompassing side walls rising from said bottom wall, angularindentations in said side walls providing for nailing the tile to aceiling, and a mass of cellular material in the space enclosed by saidwalls, said material being of lesser structural strength than thematerial of said walls and said material moulded with a plurality ofdeep cavities, one for and alined with each of the correspondingapertures in said bottom wall.

6. In combination with a ceiling, a moulded mass of sound absorbingmoulded material paralleling said ceiling and provided with a pluralityof originally moulded inwardly extending deep cavities dividing saidmaterial into a plurality of interconnected depending curtains of saidmaterial providing vertical sound absorbing surfaces of a total areagreater than the area of the ceiling occupied by said material and meansfor retaining said material comprising a sheet of metal perforated sothat the remaining metal is distributed coextensively of the bottomedges of said curtains and means for securingsaid perforated sheetrelative to said ceiling and in supporting contact with said material.

7. In combination with a ceiling, a metal box comprising a perforatedbottom wall and integral side walls, a porous sound-absorbing materialmoulded in said box and provided with a plurality of cavities extendingeach from a corresponding perforation of said bottom wall inwardly ofthe box, a more dense material moulded in the top of said box forming asubstantially integral top wall to said box, and means holding said topwall of said box in contiguity with said ceiling.

8. In combination with a ceiling, a metal box comprising a perforatedbottom Wall and integral side walls, a porous sound-absorbing materialmoulded in said box and provided with a plurality of cavities extendingeach from a corresponding perforation of said bottom wall inwardly ofthe box, a more dense material moulded in the top of said box forming asubstantially integral top wall to said box, and means holding said topwall of said box in contiguity with said ceiling, comprising a naildriven through one of said apertures and the corresponding cavitythrough said porous material and said top wall until the nail shall havebecome obscured.

9. In an acoustic tile, a polygonal box comprising a bottom wall andvertical side walls, a plurality of perforations in said box each of thesame shape as said box and arranged so that the remaining material inthe bottom wall of said box is divided into a plurality ofinterconnecting strips of uniform width, the total area of said stripsbeing less than the total area of the perforated areas of said bottomWall, and a sound absorbing material moulded in said box with deepcavities, one for and communicating with each perforation whereby thesaid material is divided into a plurality of depending interconnectedcurtains of greater depth than thickness.

10. In a sound absorbing body, the combination of a perforated thin andrelatively rigid sheet of surface material, a porous sound absorbingcellular structure normally unsuited t0 direct exposure supportedthereby in contiguity therewith, said structure having deep cavitiesmoulded therein; one for and aligned with each perforation, and meansfor retaining said struc ture in position with respect to saidperforated sheet. 1

l 11. In a sound absorbing body, the combination of a perforated thinand relatively rigid sheet of surface material, a porous sound absorbingcellular structure normally unsuited to direct exposure supportedthereby and in contiguity therewith, said structure having deep cavitiesmoulded therein; one for and aligned with each perforation and of thesame diameter as the corresponding perforation at the plane of thesheet, and means for retaining said structure with respect to saidsheet.

12. In a sound absorbing body, the combination of a perforated thin andrelatively rigid sheet of surface material, a porous sound absorbingcellular structure normally unsuited to direct exposure supportedthereby and in contiguity therewith, said structure having deep cavitiesmoulded therein; one for and aligned with each perforation and of thesame diameter as the corresponding perforation at the plane of thesheet, and means for retaining said structure with respect to saidsheet; the said structure being of limited structural strength andnormally unsuited for direct exposure.

HERBERT C. SMITH.

